/*
 * Copyright © 2014 Cask Data, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package co.cask.cdap.common.zookeeper.coordination;

import com.google.common.base.Function;

import javax.annotation.Nullable;

/**
 * A function to modify a {@link ResourceRequirement}.
 */
public interface ResourceModifier extends Function<ResourceRequirement, ResourceRequirement> {

  /**
   * Called to produce a new {@link ResourceRequirement}.
   *
   * @param existingRequirement The existing requirement or {@code null} if no existing requirement
   * @return The new requirement to submit or {@code null} if no modification wanted to be made
   */
  @Nullable
  @Override
  ResourceRequirement apply(@Nullable ResourceRequirement existingRequirement);
}
